The use of fatty acid N-alkylpolyhydroxyalkylamides and, in particular, of fatty acid N-methylglucamide is already known from DE-A-4 430 085; DE-A-4 326 950; DE-A-4 432 366; DE-A-4 424 823; WO 92/6153; WO 92/6156; WO 92/6157; WO 92/6158; WO 92/6159 and WO 92/6160. As well as their high detergency, important advantages of the fatty acid N-methylglucamides are their good biodegradability and the fact that they can be prepared from renewable raw materials. The use of this group of substances as thickeners is also known (EP-A-285 768).
A disadvantage for the use and formulation is the limited solubility of these substances, particularly those having a chain length greater than C16. At relatively high concentrations in water they can only be handled with difficulty because of their high viscosity. Relatively high temperatures, which reduce the viscosity, however, lead to increased hydrolysis.
DE-A-4 238 207 and DE-A-4 238 211 disclose the use of fatty acid polyhydroxyalkylamides as surfactants, which differ from the previously mentioned fatty acid N-alkylpolyhydroxyalkylamides by virtue of the fact that the alkyl group is substituted by a dialkylamino group. Furthermore, these sugar surfactants are quaternized.